The nut and bolt look like the style that is used for the attachment points of the power steering pump to its mounting bracket (bolts go through straps and rubber bushings). I will see if I can find a photo. Is there any hardware missing from the PS pump mount points?
One way I have found to see where the VW/Audi part of the engine ends and the Volvo car interface begins is with the hardware used. The VW hardware typically involves regular non-shouldered hex bolts with 10mm or 13mm heads and flat washers. Meanwhile Volvo appeared to favor flange bolts like the one your picture shows, with no washer used, and a 10mm, 12mm, or 14mm head. Thus when working on or inside the engine itself you will have 10mm and 13mm tools in use, but if you need to get out a 12mm or 14mm tool, that suggests you are dealing with an external "vehicle integration" part of the engine where Volvo added its own parts to adapt the engine into its cars. Power steering/AC/alternator mounting, motor mounts, throttle and cruise linkage, electrical ground or harness attachments, etc are where this type of hardware will be used.
Trying to put something back together that someone else took apart is always a challenge. I have enough trouble with stuff I myself took apart then try to reassemble years later, let alone when someone else did it. Sounds like you are making great progress, will be fun to hear how it runs after many years.
The CS device is not critical to getting the engine running but you do need to get it into the fully retracted position in order to correctly set the static injection timing. If needed you could disconnect or remove the cable linkage and then internal spring pressure should retract it into the warm position when you spin the pump a few times. In temperate weather it will start fine without the CSD functioning and once you have it running and warmed up you can get the linkage reinstalled and dialed in.